I've looked all over the threads here and suprising don't see an answer to this question. Also the FSM and Haynes don't seem to have numbers on that. So here goes....

I'm still in the process of getting a '91 I bought up and running well. I have it running, but it doesn't have much power. It could be a bunch of things, but I'm suspecting a manifod vacuum leak, because it has a rough idle too. The vacuum I get at the manifold at idle it -12 in/Hg (which seems low). Punching the throttle, the vacuum drops to 0" and then to -15. I've done a cursory look for loose/cracked hoses, but all look fine.

My main question is WHAT is considered GOOD idle vacuum for that car?

 

12in HG is quite low. 15 is about average for "acceptable range" and 16-17 is about normal for fresh rebuilds.

 

Thank you Integra. I guess I'll start looking harder for a leak this evening. Hope it's just something that simple.... (:>